This application is a 371 of PCT/CH03/00028 filed on Apr. 08, 2003.
1. Field of the Invention
The present invention relates to the field of antenna technology and, more particularly, to a dual-band antenna.
2. Description of the Related Art
The rising demand for data to be transmitted in the area of mobile radio has led to the definition of the UMTS (Universal Mobile Telecommunication System) standard in the past. Applications based on this standard require a new mobile radio network. A component of this network are antennas which must also be newly developed since the UMTS standard is based on new frequency ranges for transmitting and receiving. The previous mobile radio networks according to the conventional GSM 900/1800 standard, and a number of other networks conforming to other standards, will continue to be operated in parallel with the newly created UMTS standard for a period which cannot yet be predicted. To achieve the construction of a UMTS network which is as rapid as possible, network operators are interested in using existing antenna sites both for the existing networks and to be integrated into the new UMTS network. The development of antennas which cover both the frequency ranges of existing networks and the UMTS frequency ranges enables network operators to shorten the time for the licensing procedures or to cut it out altogether. Furthermore, it is possible to assume that the public acceptance of an individual antenna which covers all locally used mobile radio standards will be higher in comparison with different individual antennas for each standard.
Dual-polarized antennas for base stations consisting of an array of dual-polarized individual radiators (single antennas) have been known for a long time. Similarly, dual-polarized broadband antennas are known which are composed of an array of identical dual-polarized individual radiators which are tuned to frequencies of 1710–2170 MHz over a wide band so that the antenna covers both the GSM 1800 band and the UMTS band. A particularly effective individual radiator of this type which has been successful in practice is known from WO-A1-01/76010. Furthermore, dual-polarized antennas are known which cover the GSM 900 band and the GSM 1800 or GSM 1800/UMTS band and which consist of an array of correspondingly tuned dual-polarized individual radiators.
In U.S.-B1-6,211,841, a multi-band antenna for mobile radio base stations has been proposed in which the frequency bands of GSM 900, GSM 1800 and UMTS are covered by a combination of two arrays with two different individual radiators in the form of crossed dipoles (low-band dipoles, high-band dipoles).
In WO-A2-99/59223, a dual-band antenna is disclosed in which a first linear array of patch radiators for the GSM band (860–970 MHz) is combined with a second linear array of crossed dipoles for the PCN band (1710–1880 MHz), the crossed dipoles being arranged between the patch radiators in a first embodiment and directly above the patch radiators in a second embodiment.
In U.S.-B1-6,239,750, an antenna arrangement for multi-band operation is proposed in which (FIG. 4) two linear arrays of two different patch radiators are combined with one another, the first patch radiators being tuned to the frequency band of 1800–1900 MHz and the second patch radiators being tuned to the frequency band of 800–900 MHz and the first patch radiators being arranged alternately between and directly above the second patch radiators.
To be able to use, on the one hand, the existing antenna spaces at the base stations equally for the previous bands and the new UMTS band and, on the other hand, utilize the advantages of the individual radiator developed by the applicant according to WO-A1-01/76010, it was desirable to use these individual radiators in a dual-band antenna.
It would, therefore, be desirable to create a broadband dual-band antenna which is suitable both for the GSM 900 band and for the GSM 1800 and UMTS band and is based on an individual-radiator type as has been disclosed in WO-A1-01/76010.